Giant Molecular Association in Spiral Arms of M 31: I. Evidence for Dense Gas Formation via Spiral Shock Associated with Density Waves?

Details Giant Molecular Association in Spiral Arms of M 31: I. Evidence for Dense Gas Formation via Spiral Shock Associated with Density Waves? Giant Molecular Association in Spiral Arms of M 31: I. Evidence for Dense Gas Formation via Spiral Shock Associated with Density Waves?

Feb 2007

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007pasj...59...33t&link_type=abstract

Publications of the Astronomical Society of Japan, Vol.59, No.1, pp.33-42

Astronomy and Astrophysics

Astronomy

8

Galaxies: Individual (M31), Ism: Molecules, Stars: Formation

Scientific paper

We present observations of 12CO (J = 1-0), 13CO (J = 1-0), and 12CO (J = 3-2) emissions toward a Giant Molecular Association (GMA) in the southern spiral arm of M 31 using the NRO 45 m and the ASTE 10 m telescopes. Observed regions are 3' × 4' (0.6 kpc × 0.8 kpc) with an angular resolution of 16''-17'' for 12CO (1-0) and 13CO (1-0), and 1.2' × 1.4' with 23'' for 12CO (3-2). The GMA has a size of a few 100 pc and a mass of 5.6×106 M_odot. The 12CO (1-0) to 13CO (1-0) integrated intensity ratio (R12/13) and the 12CO (3-2) to 12CO (1-0) ratio (R3-2/1-0), averaged over the entire region of the GMA, are ˜ 10 and 0.3, respectively. These line ratios suggest gas densities of (3-6) × 102 cm-3 at a temperature of 15-25 K, which are similar to, or slightly larger than, those of GMCs in the Galactic disk. We found a radial gradient of R12/13 within the GMA, ranging from 6 at the center to 14 at the edges. The distribution of R12/13 shows a smooth structure with an overall density gradient. The GMA consists of two velocity components, blue (˜ -505 km s-1) and red (≥-490 km s-1). In both the 12CO (1-0) and 13CO (1-0) profiles, the blue component shows a strong peak intensity and a narrow velocity width, while the red is weaker and wider. The R12/13 value of the red component is 5 and that of the blue is 16, indicating that the red component has a higher gas density. Moreover, we suggest that the red component is ``post-shock'' dense gas decelerated by shock due to the density wave.

Affiliated with

Also associated with

No associations

Rating

Giant Molecular Association in Spiral Arms of M 31: I. Evidence for Dense Gas Formation via Spiral Shock Associated with Density Waves? does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Giant Molecular Association in Spiral Arms of M 31: I. Evidence for Dense Gas Formation via Spiral Shock Associated with Density Waves?, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Giant Molecular Association in Spiral Arms of M 31: I. Evidence for Dense Gas Formation via Spiral Shock Associated with Density Waves? will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1156402